There is a popular hope, nurtured by futurists like Elon Musk and Craig Venter, that with the right ingredients, Mars can be terraformed into a kind of a paradisiacal facsimile of Earth.
"It's a fixer-upper of a planet," Musk told Stephen Colbert on a recent episode of The Late Show. "First you have to live in transparent domes, but eventually you can transform it into an Earthlike planet."
This is a captivating vision of the future and one that by no means deserves discouragement. But according to NASA astrobiologist Lynn Rothschild, a specialist in synthetic biology, we shouldn't pin all of our Martian dreams on terraforming alone.
"Terraforming is making a planet Earthlike," Rothschild told me over the phone. "I think the chance of making Mars like the Earth—an exact replica—is pretty bad."
A more precise word, Rothschild said, would be "ecopoiesis," which refers to the process of seeding a new ecosystem into a sterile environment. It's like a scaled down version of terraforming that can be localized to certain regions—for instance, the Palikir crater where the latest evidence of flowing water was found.
"What I think is the most likely for the foreseeable future is having small areas that are enclosed," Rothschild said. "Once you establish a smaller enclosed area, then you can start talking about recycling oxygen through algae, and all the stuff we're working on."
"I think the chance of making Mars like the Earth—an exact replica—is pretty bad."
"But there's a huge leap between that and setting up an atmosphere with 21 percent oxygen, when it took algae on the Earth about a billion years to get there," she added.
Still, successful ecopoiesis on Mars, even if restricted to a local scale, would be a major step in the road to human colonization, and Rothschild is optimistic that it will one day be achieved with the help of synthetic lifeforms.
"Going forth from planet Earth, synthetic biology will be even more important, because now you're dealing with environments in which nothing has evolved," she told me. "If you're on Mars, it's a lot colder and there's more radiation. Synthetic biology has the potential to make organisms that are more resistant to radiation or temperature extremes or whatever."
"We're already doing some of that in my lab and have been for a couple years," she continued, referencing an ongoing project called "Hell Cell," in which she and her students cook up artificial extremophiles that can theoretically survive interplanetary conditions.
"When we start to think about it that way, that is something that synthetic biology will do—I don't even think it is 'can do,' but will do—that really is our lives in the future on planet Earth and off planet Earth," she said. "If we want to breed hardier plants, with a better temperature tolerance, or ones that pull more carbon dioxide from the atmosphere, we can start to go in and do that."
To that end, this kind of technology is as relevant to keeping our own planet liveable as it is to boosting the habitability of other worlds. Space exploration, after all, has a long history of influencing technologies on Earth, and the development of hardier synthetic organisms may be the next giant leap along those lines.
"A great example actually, being that I'm in California, is the drought and the issue of running out of fresh water," Rothschild said. "Now, we do happen to have a lot of water in the Pacific Ocean. so what if instead of growing your alfalfa or rice with fresh water, you could mix it fifty-fifty with sea water?"
"Just make plants more salt tolerant," she continued. "There are lots of organisms that are halophiles—ones that live in very high concentrations of salt—and there are a couple tricks to the trade that these organisms use. I don't really see why it should be impossible, or even potentially that difficult, to make a rice plant that could live on 50 percent salt water."
In this way, Earth's dwindling resources and Mars's perilous conditions can be overcome by carefully constructed synthetic ecologies. Natural selection has gotten us this far, but in order to ensure our long-term survival—here on this planet and beyond it—we will have to take evolution into our own hands.